Update UIA aria-readonly mappings

[sivakusayan]

Closes #127

The UIA aria-readonly mappings only accounted for controls that implemented the IValueProvider interface. Now, it also accounts for controls that implement the IRangeValueProvider, and otherwise puts the information in AriaProperties if a control implements neither IValueProvider nor IRangeValueProvider.

Implementation

• WPT tests: Add aria-readonly=true UIA tests web-platform-tests/wpt#41904
• Implementations (link to issue or when done, link to commit):
  • WebKit: N/A
  • Gecko: N/A, no UIAutomation support.
  • Blink: Commit. Here is the current code. Full support, although Chromium does seem to implement certain UIAutomation patterns (I think) unnecessarily, but functionally everything seems correct.

As an aside, if you want to observe this mapping in Blink, you'll need to use Edge or run Chromium with UIAutomation enabled - the UIAutomation bridge will not map IA2 STATE_SYSTEM_READONLY to the AriaProperties property when appropriate.

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Preview | Diff

[sivakusayan]

WPT tests are added.
Blink seems to be fine functionally, although I did notice interesting behavior:

• grid, listbox, slider, and spinbutton all implement IValueProvider and expose Value.IsReadOnly, although I'm not sure if these controls are necessarily a good fit for the Value pattern if I'm understanding the documentation correctly. I'm not sure if this matters since grid/listbox additionally expose AriaProperties.readonly, and slider/spinbutton additionally expose RangeValue.IsReadOnly.
• Every control that supports aria-readonly expose AriaProperties.readonly, regardless of what providers the control implements.

This doesn't affect anything functionally as far as I'm aware, so I probably won't write up a bug report for these, but just a head's up.